Prevention: an introduction

If Willet Whitmore was alive today, he might restate his famous aphorism (about the possibility of curing prostate cancer) to address its prevention, like this:

Is prevention possible in those for whom it is necessary, and is prevention necessary for those in whom it is possible?

Doing Things That Decrease Risk

It would be good if we knew for certain that we could prevent prostate cancer by doing things that decrease risk for cancer (just like we prevent tooth decay by adding fluoride to drinking water).

Two drugs, called finasteride (Proscar) and dutasteride (Avodart), are used to shrink the prostate in men who have overly enlarged prostates. (This condition is called “benign prostatic hyperplasia”. It is not the same as prostate cancer.)

Some time ago, a very large clinical trial (the Prostate Cancer Prevention Trial) showed that one of these two drugs (finasteride) really can reduce the risk for diagnosis of prostate cancer. However, the same trial also seemed to show that use of finasteride might be increasing the risk for high-grade, biologically more dangerous tumors. More recently a second large trial (the REDUCE trial) clearly demonstrated that the other of these two drugs (dutasteride) very definitely reduced the risk for a diagnosis of prostate cancer by 23 percent in patients who met criteria for high risk of a diagnosis — but again with a slight indication of an increased risk for more dangerous tumors.

After a great deal of careful analysis and a lot of heart searching, the American Society for Clinical Oncology and the American Urological Association issued a guideline in February 2009 about the use of finasteride and dutasteride to prevent prostate cancer. The guideline recommends that men who are having regular PSA tests and physical examinations, and men who are taking finasteride or dutasteride for other reasons, should discuss the value of starting or staying on these drugs to prevent prostate cancer with their doctors. This is the first time any drug has ever been specifically recommended as having even potential value in the prevention of prostate cancer. More information about the precise recommendations of the guideline are available elsewhere on this web site. However, it should be noted that the U.S. Food & Drug Administration has not approved the use of either finasteride or dutasteride for the prevention of prostate cancer — even in men at high risk for this form of cancer.

Several studies have suggested an association between prostate cancer risk and things in the environment. Among these are exposure to sunlight, drinking red wine, α-linolenic acid, anti-inflammatory medications, and aspirin. However, these findings have not been well tested. Until they are properly tested, their proposed role in reducing prostate cancer risk is just speculation.

Some so-called “micro-nutrients” (products that occur normally in our diets in very small quantities) are being or have been studied as possible prostate cancer preventives. They include selenium, lycopene, and vitamin E (properly known as α-tocopherol). None of these micro-nutrients has been shown to prevent prostate cancer to date. Indeed, recent information has confirmed that neither selenium nor vitamin E have any clinical impact on the prevention of prostate cancer and that overuse of these compounds may be associated with increased risk of prostate cancer or diabetes.

Literally hundreds of different herbal concoctions and supplements are promoted by their manufacturers (or just their advocates) for the prevention of cancer, including prostate cancer. In the cases of very, very few of these products is there any good clinical evidence to even suggest the possibility of effectiveness, and none of them have ever been shown to have such an effect in a randomized, double-blind, placebo-controlled trial. Before using any of these agents to prevent prostate cancer, we strongly suggest that you refer to information about these products on the most reliable medical resource that we know to be available: the section “About Herbs, Botanicals, and Other Products” developed by the Department of Integrative Medicine on the website of the Memorial Sloan-Kettering Cancer Center.

Avoiding Things That Increase Risk

It would also be great if we could prevent prostate cancer by stopping doing things that increase risk for the disease (just as you can lower your risk for lung cancer by not smoking cigarettes). Two good examples are eating less red meat and fewer fatty foods. While the evidence is not absolutely compelling, there is certainly a great deal of suggestive evidence of an association between prostate cancer risk and consumption of a diet high in red meat and high-fat foods.

Cadmium smelting is absolutely associated with increased risk for prostate cancer, and there is some significant evidence that exposure to Agent Orange, a defoliant used in the Vietnam war, may also be associated with prostate cancer risk (although the American Cancer Society states that this evidence is “not compelling”). You should definitely avoid exposure to cadmium and Agent Orange, however, because exposure to Agent Orange has been associated with risks for other forms of cancer. If your work involves the possibility of exposure to these products, appropriate precautions should be taken to minimize your exposure.

Some dietary supplements may contain unlisted ingredients, including testosterone, that have potent growth effects on prostate cells. Not so long ago, two men died of prostate cancer. Both had normal prostates not long before coming to the doctor with widely spread prostate cancer. Both had taken the same over-the-counter supplement to enhance muscle strength and sexual performance. The manufacturer took the supplement off the market.

Dietary supplements are not regulated in the same way as drugs are. Because of this, supplements have the potential to cause great harm. Among recent examples are the supplements Ephedra, which was associated with death, and PC-SPES, which was contaminated with blood thinners and also associated with death. Lots of men use dietary supplements, and we just don’t know whether prostate cancer development is being stimulated by such supplements. However, the problem could be enormous. Again, before using any herbal, botanical, or supplement for the prevention or treatment of prostate cancer, please see the section “About Herbs, Botanicals, and Other Products” developed by the Department of Integrative Medicine on the website of the Memorial Sloan-Kettering Cancer Center.

Content on this page last reviewed and updated March 26, 2011